DomainKeys Identified Mail, or DKIM, is a method for confirming the legitimacy of an email message using an e-signature. When DomainKeys Identified Mail is activated for a certain domain, a public cryptographic key is published to the global DNS database and a private one is kept on the mail server. When a new message is sent, a signature is issued using the private key and when the email message is received, that signature is validated by the receiving server using the public key. In this way, the recipient can easily tell if the email message is legitimate or if the sender’s email address has been forged. A discrepancy will occur if the content of the email has been changed in the meantime as well, so DomainKeys Identified Mail can also be used to make sure that the sent and the received email messages are identical and that nothing has been attached or erased. This email authentication system will increase your email security, as you can verify the legitimacy of the important email messages that you get and your colleagues can do the same with the email messages that you send them. Based on the given email provider’s adopted policy, an email message that fails the test may be erased or may be delivered to the recipient’s inbox with a warning symbol.